Editors' Choice

Science  26 Sep 2014:
Vol. 345, Issue 6204, pp. 1575
  1. Neuroscience

    Timing counts for whisker development

    1. Peter Stern
    PHOTO: © 2/LIFE ON WHITE/OCEAN/CORBIS

    Whiskers help animals to sense the world around them. Each whisker precisely connects to a specific area of the brain. These connections form during early brain development, and protein receptors that bind to the neurotransmitter glutamate (specifically, NMDA-type glutamate receptors) play a key role in their refinement. Fetal and neonatal brains express subunits of the NMDA receptor that regulate its function, called GluN2B and GluN2D. Yamasaki et al. discovered that GluN2B and GluN2D play opposing roles as whisker-brain connections develop and mature in mice. Connections formed nearly a day early when mice lacked GluN2D expression. In contrast, reduced expression of the GluN2B subunit delayed the development of the connections by a day.

    J. Neurosci. 34, 11534 (2014).

  2. Neuroscience

    Animal behavior follows dopamine rewards

    1. Peter Stern

    In auditory fear conditioning, mice learn to associate auditory cues, such as a tone, with mild footshocks. Forming associations like this, then remembering them long-term (called fear memory consolidation), is an important strategy for navigating one's environment. To understand the molecular basis of fear memory consolidation, Dias et al. investigated the contribution microRNAs, small bits of RNA that modulate gene expression. They discovered an important role for the microRNA-34a, which targeted components of a particular signaling pathway (the so-called Notch pathway) that is normally involved in development. MicroRNA-34a caused a transient decrease in Notch-dependent signalling in the amygdala, which was important for fear memory consolidation.

    Neuron 83, 906 (2014).

  3. Phagocytosis

    Bring out your dead — hungry receptors await

    1. Stella M. Hurtley

    Every day billions of cells die within the body. Specialized cells called phagocytes patrol the blood and act as cellular garbage collectors, clearing dead cells to prevent tissue damage and inflammation. Phagocytes recognize dead cells because they express molecular “eat me” signals on their surfaces. Zagórska et al. examined how mouse phagocytes use different cellular protein receptors, called TAMs, during this process. The TAM receptors Mer and Axl recognize the “eat me” signals on the surface of dead cells. Mer kept the peace by removing the dead cells that accumulate during normal wear and tear. In contrast, during inflammation, Axl protein expression increased and it took over the removal process from Mer.

    Nat. Immunol. 10.1038/ni.2986 (2014).

  4. Marine Ecology

    An Arabian wintertime bloom on the rise

    1. H. Jesse Smith

    The bioluminescent dinoflagellite Noctiluca scintillans

    PHOTO: VISUALS UNLIMITED, INC./WIM VAN EGMOND

    Large and widespread wintertime blooms of the dinoflagellate Noctiluca scintillans have begun to occur in the Arabian Sea. Until a decade ago, wintertime blooms there were dominated by diatoms, unicellular photosynthetic organisms that thrive in the abundant sunlight and high-nutrient conditions which occur at that time of the year. Now those diatoms are being outcompeted. Gomes et al. report that a decrease in the oxygen content of surface waters probably has caused this change, which itself may be caused by high fluxes of organic matter from domestic and industrial wastes. The ascendance of Noctiluca scintillans could have a negative impact on the fisheries of the Arabian Sea, which are sustained by the diatom blooms that now are being disrupted by this new order.

    Nat. Commun. 10.1038/ncomms5862 (2014).

  5. Social Interactions

    Hate and violence spread through the air

    1. Brad Wible

    During the 1994 Rwandan genocide, radio station RTLM aired racist propaganda promoting violence against Tutsis. We now can see quantitatively some of the effects of this propaganda. Yanagizawa-Drott modeled radio signal propagation across this “land of a thousand hills” to determine which villages could receive the RTLM signal. Then they compared their map with court records of the number of people in each village later prosecuted for violent crimes during the genocide. They found that RTLM radio reception was associated with an increase in violence. Militia violence was higher when neighboring villages also had radio coverage, suggesting that social interactions promoted the diffusion of organized violence. The authors estimate that RTLM was responsible for 10% of the total participation in the genocide, by roughly 51,000 people.

    Quart. J. Economics 10.1093/qje/qju020 (2014).

  6. Ornithology

    Social complexity creates brainy parrots

    1. Virginia Morell

    Monk parakeets' relationships are key to their smarts.

    PHOTO: © LÉLIA VALDUGA/ALAMY

    A complex social world of shifting alliances and competitors may be key to the evolution of large brains in humans, dolphins, and spotted hyenas – and, researchers now say, parrots. Hobson et al. observed wild populations of monk parakeets (Myiopsitta monachus) in Argentina and captive ones in Florida, finding that the parakeets prefer to spend time with one individual, usually a mate. Captive birds had strong associations with one or two individuals and numerous moderate relationships; their aggressive interactions also suggest a dominance hierarchy of winners and losers. Those layers of relationships require the birds to recognize and remember others—tasks linked to the evolution of cognitive skills.

    Auk. 10.1642/AUK-14-14.1 (2014)

  7. Medicine

    Teaching tolerance stops the bleeding

    1. Lisa D. Chong

    People with hemophilia A lack a clotting factor [factor VIII (FVIII)] that stops wounds from bleeding. Regular infusions of FVIII can help, but up to 30% of patients make antibodies that attack this treatment. To prevent this, Sherman et al. developed a way to teach the immune system to tolerate FVIII, rather than makes antibodies against it. For 2 months, the researchers fed mice leaves from plants engineered to produce fragments of FVIII. The fragments, safely encapsulated in plant cells, entered the area of the gut where immune cells reside and reduced the immune response to FVIII. Treated mice made fewer antibodies against FVIII, suggesting that teaching (immune) tolerance may allow FVIII to stick around and do its job.

    Blood 123, 10 (2014).

  8. Catalysis

    Constructing a maze full of phosphines

    1. Jake Yeston

    The manufacture of commodity chemicals relies on metals to catalyze, or speed along, the process of making and breaking bonds between lighter elements such as carbon and oxygen. In many cases, the metals are bound to a supporting material to facilitate their separation from the product stream and their subsequent reuse. However, it can be challenging to adopt this approach when the catalyst structure incorporates metalphosphorus coordination. Sun et al. prepared a porous solid by linking phosphine building blocks together. When they introduced rhodium into the structure, the resulting material catalyzed the hydroformylation reaction of octene as well as a free-floating rhodiumphosphine complex.

    Chem. Commun. 10.1039/C4CC03884C (2014).

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